RF communication system having a chaotic signal generator and method for generating chaotic signal

ABSTRACT

A radio frequency (RF) communication system having a chaotic signal generator and a method of generating a chaotic signal. The RF communication system includes a chaotic signal generator which generates a chaotic signal having a plurality of frequency components at a predetermined frequency band, a modulator which generates a chaotic carrier by combining the chaotic signal with a data signal which indicates information, and a transmission circuit which includes an antenna to transmit the chaotic carrier made at the modulator. The frequency signal generator comprises an oscillator which converts a DC bias power into a high frequency power, and a resonating unit which generates a wideband signal having a plurality of frequency components by passing a predetermined frequency band of the high frequency power signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2006-0018210, filed Feb. 24, 2006, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Systems and methods consistent with the present invention generallyrelate to a radio frequency (RF) communication system having a chaoticsignal generator and a method of generating a chaotic signal, and moreparticularly, to an RF communication system having a chaotic signalgenerator which is less power-consuming, small in size and easy toconstruct and a method of generating a chaotic signal.

2. Description of the Related Art

A spread-spectrum communications technique transmits signal using a muchwider band than the bandwidth of the signal. A representative example ofusing this technique is a code division multiple access (CDMA) whichuses narrowband carriers. Additionally, there also is a way of usingwideband carriers.

In order to use narrowband carriers, frequency of the data fortransmission is modulated to be narrower than the frequency band of thecarrier signal, while the frequency band of the data for transmission ismodulated to be wider than the frequency band of the carrier signal inorder to use wideband carriers.

Carriers in the spread-spectrum communications usually use sinuous wavesand pulses. The sinuous waves or pulses are up-converted to a certainfrequency to transmit data. To this end, a transmitter of acommunication system needs components for up-converting the carriersfrom a baseband to a certain frequency band, while a receiver needscomponents to down-convert the received carriers back to the baseband.

More specifically, the transmitter includes a voltage controlleroscillator (VCO) to generate a frequency to transmit data, and a phaselocked loop (PLL) to lock the generated frequency from externalinfluence. The transmitter also requires an up-mixer to up-convert thebaseband carriers at the frequency generated by the VCO.

Accordingly, the receiver requires a down-mixer to down-convert thereceived carriers back to baseband.

Because the transmitter has components such as VCO, PLL, and up-mixer,power consumption increases. Additionally, components such an up-mixeris quite large and therefore, the size of the transmitter alsoincreases. Likewise, there usually is a big and power-consuming receiveras the receiver uses components such as a down-mixer.

IEEE 802.15.4a standard has proposed the use of chaotic signals totransmit data.

IEEE 802.15.4a is the Task Group for the standardization of low-ratenavigation sensor network, which proposed a next-generationcommunication incorporating a hybrid of IEEE 802.15.4 ZigBee and IEEE802.15.3 Ultra Wide Band (UWB) communications with the functions ofnavigation and low-rate power consumption.

The chaotic signal modulation has been proposed in an attempt to achievelow-rate power consumption. The chaotic signal modulation can bedesigned in a simple RF structure at the hardware level, and circuits,which are generally required for an RF communication system such as VCO,PLL and mixer, are not necessary. Accordingly, power consumption can bereduced to 5 mW one-third of general power consumption, by using thechaotic signal modulation.

Therefore, a low-rate RF communication system will be achieved, if achaotic signal modulation is appropriately applied.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention overcome the abovedisadvantages and other disadvantages not described above. Also, thepresent invention is not required to overcome the disadvantagesdescribed above, and an exemplary embodiment of the present inventionmay not overcome any of the problems described above.

The present invention provides a low-rate RF communication system havinga chaotic signal generator, and a method of generating chaotic signal.

According to one aspect of the present invention, the present inventionprovides an RF communication system comprising: a chaotic signalgenerator which generates a chaotic signal having a plurality offrequency components at a predetermined frequency band; a modulatorwhich generates a chaotic carrier by combining the chaotic signal with adata signal which indicates information; and a transmission circuitwhich includes an antenna to transmit the chaotic carrier made at themodulator.

The chaotic signal generator may comprise an oscillator which converts adirect current (DC) bias power into a high frequency power, and aresonating unit which generates a wideband signal having a plurality offrequency components by passing a predetermined frequency band of thehigh frequency power signal.

The resonating unit may comprise a first filter which receives the highfrequency power from the oscillator and passes at least a part of aharmonic signal of the high frequency power; and a second filter whichgenerates a wideband signal having a plurality of frequency componentsof a predetermined range of frequency band by oscillating the filteredsignal, and provides the oscillator with the wideband signal.

The oscillator may comprise a nonlinear element, and high frequencypower of the nonlinear element is determined by:

${f(z)} = {M\left\lbrack {{{z + e_{1}}} - {{z^{\prime} - e_{1}}} + \frac{{{z - e_{2}}} - {{z + e_{2}}}}{2}} \right\rbrack}$

where, M is an amplifier constant of the nonlinear element, and e₁, e₂are constants.

The nonlinear element comprises one of a transistor and a diode.

The signal generator may be oscillated when the conditions are met thatthe phase of a signal passing a loop of the nonlinear element, the firstfilter and the second filter is a multiple of 2π.

The signal generator may be oscillated when the conditions are met thata total gain of the loop is larger than 1.

The signal outputted from the first filter may be determined by:

Tx ₁ ′+x ₁ =f(z _(N))

where, f(z_(N)) is the function of high frequency output from thenonlinear element, T is a time constant of the first filter, and x₁ isthe initial signal outputted from the first filter.

The first filter may comprise a low pass filter (LPF), and the firstfilter may be a primary filter.

The second filter may comprise at least one band pass filter (BPF), andthe BPF may preferably be a secondary filter.

A (N)th output from the BPF may be determined by:

z _(N)″+α_(BN) z _(N)′+ω_(BN) ² z _(N)=ω_(BN) ² z′ _(N−1)

where, z_(N−1) is an output from the (N−1)th BPF, that is, an input tothe (N)th BPF, α_(BN) is an attenuation constant, ω_(BN) is a resonatingfrequency and z_(N) is an output from the (N)th BPF.

The BPF may determine a resonating frequency band of the chaotic signalgenerator.

The second filter may comprise at least one LPF, and the LPF of thesecond filter may be a secondary filter.

The LPF of the second filter may be disposed between the first filterand the BPF.

An output from the (M)th LPF of the second filter may be determined by:

y _(M)″+α_(LM) y′ _(M)+ω_(LM) ² y _(M)=ω_(LM) ² y _(M-1)

where, y_(M-1) is an output from the (M−1)th LPF, that is, an input tothe (M)th LPF, α_(LM) is an attenuation constant, ω_(LM) is a resonatingfrequency, and y_(M) is an output from the (M)th LPF.

The LPF and the BPF of the second filter may have different delayedphase widths and gains, respectively.

The second filter may comprise a predetermined number of LPFs and BPFsso that a phase of a signal passing a loop of the nonlinear element, thefirst filter and the second filter corresponds to a multiple of 2π.

According to an aspect of the present invention, an RF communicationsystem may be provided, comprising a nonlinear element which converts aDC bias power into a high frequency power; a first LPF which filters thehigh frequency power into a predetermined frequency band; one or moresecond LPFs which shift the filtered high frequency power according to apredetermined phase width; and one or more BPFs which have differencephase widths than the second LPFs, and filter the shifted signal into apredetermined frequency band.

The BPF may comprise first to third BPFs.

According to another aspect of the present invention an RF communicationsystem may be provided, comprising an oscillator which converts a DCbias power into a high frequency power; and a resonating unit whichgenerates a wideband signal having a plurality of frequency componentsby passing a predetermined frequency band of the high frequency powersignal.

According to yet another aspect of the present invention, and RFcommunication system may be provided, comprising: a nonlinear elementwhich converts a DC bias power into a high frequency power; a firstfilter which receives a high frequency power from the nonlinear elementand passes at least a part of a harmonic signal of the high frequencypower; and a second filter comprising one or more LPFs and one or moreBPFs, which generate a wideband signal having a plurality of frequencycomponents in a predetermined range of frequency band by oscillating asignal from the first filter, and provide the nonlinear element with thewideband signal.

According to yet another aspect of the present invention, a method ofgenerating a chaotic signal in an RF communication system, comprising:converting a DC bias power into a high frequency power; generating aninitial signal which meets initial conditions for oscillation using thehigh frequency power; and generating a wideband signal having aplurality of frequency components in a predetermined range of frequencyband by oscillating the initial signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will be moreapparent by describing certain exemplary embodiments of the presentinvention with reference to the accompanying drawings, in which:

FIG. 1 shows a block diagram of a transceiver of a RF communicationsystem using chaotic signal, and graphical representations of signalwaves in respective domains of the RF communication system;

FIG. 2A shows, in enlargement, waves of chaotic signals generated from achaotic signal generator of FIG. 1;

FIG. 2B shows a graphical representation showing the chaotic signal ofFIG. 2A based on frequency domain;

FIG. 2C is a graphical representation of an enlarged data signal;

FIG. 2D shows a graphical representation of chaotic carrier bymodulating the chaotic signal of FIG. 2A and the data signal of FIG. 2C;

FIG. 2E is a graphical representation of the chaotic carrier of FIG. 2Dbased on frequency domain;

FIG. 3 is a graphical representation of a frequency bandwidth of achaotic signal region 1 T and a pulse region 3 T;

FIG. 4 is a block diagram of a chaotic signal generator according to anexemplary embodiment of the present invention;

FIG. 5 is a block diagram of a chaotic signal generator according to anexemplary embodiment of the present invention;

FIG. 6 is a graphical representation of chaotic signal generated fromthe chaotic signal generator based on the time domain;

FIG. 7 is a graphical representation of the result of measuring powerspectrum density of chaotic signal according to an exemplary embodimentof the present invention;

FIG. 8A is a graphical representation of an example of a signal maskdefined by the Federal Communications Commission (FCC);

FIG. 8B shows a power spectrum of chaotic signal generated by a chaoticsignal generator based on the mask of FIG. 8A;

FIG. 9A is a graphical representation of time domain of chaotic carrierwhich combines the chaotic signal of FIG. 6 with the data signal; and

FIG. 9B is a power spectrum of chaotic carrier of FIG. 9A.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The exemplary embodiments are described below in order toexplain the present invention by referring to the figures.

The matters defined in the description such as the detailed constructionand elements are provided to assist in a comprehensive understanding ofthe invention. Thus, it would be apparent to one skilled in the art thatthe present invention can be practiced out without those definedmatters. Also, well-known functions or constructions are not describedin detail since they would obscure the invention with unnecessarydetail.

The present invention particularly relates to the structure andoperational principle of a RF communication system using a chaoticsignal, and a chaotic signal generator to generate the chaotic signal.

The ‘chaotic signal’ particularly refers to a carrier used in thetransmission of data signal between a transceiver, and the chaoticsignal is directly generated in the frequency band for data signaltransmission.

FIG. 1 shows a block diagram of a transceiver of a RF communicationsystem using a chaotic signal, along with the waves at points (a) to(g).

The transceiver of a RF communication system may include a transmissioncircuit 10 which transmits a chaotic carrier which is obtained bymodulating a chaotic signal and data signal, and a reception circuit 20which receives the chaotic carrier and evaluates the data signal. Thetransceiver may also include a transmission/reception antenna 5, aswitch 7 which connects one of the transmission circuit 10 and thereception circuit 20 to the antenna 5, and a band pass filter (BPF) 6which filters the transmitted or received chaotic carrier.

The transmission circuit 10 may include a chaotic signal generator 30, amodulator 11, and a power amplifier 15.

The chaotic signal generator 30 may generate a chaotic signal which hasa plurality of frequency components in a predetermined frequency band.With reference to point (d) of FIG. 1, the chaotic signal is generatedas a plurality of pulses with different periods and amplitudes in thetime domain are successively generated. FIG. 2A shows an enlargedchaotic signal at point (d) of FIG. 1. Based on the frequency domain,the chaotic signal is spread widely along the predetermined frequencyband as show in FIG. 2B. The frequency band for the chaotic signal mayvary according to the design of the chaotic signal generator 30, andFIG. 2B shows the chaotic signal spreading along the UWB from about 3.1GHz to about 5.1 GHz.

The frequency band of the chaotic signal is determined by the frequencybandwidth of the chaotic signal which is generated from the chaoticsignal generator 30, and is not related with the pulse region T of thechaotic signal. As shown in FIG. 3, the frequency bandwidth Δf is almostidentical as the wideband property of the carrier, either when the pulseregion of the chaotic signal is 1 T or when it is 3 T. Because the samefrequency bandwidth can be maintained irrespective of the variance ofpulse region of the chaotic signal, there is no need for additionalcomponents such as filter or amplifier to change the pulse region.Furthermore, even the carrier of stronger energy can be transmitted andreceived by changing the pulse region of the chaotic signal.Accordingly, the communication range can be adequately controlledwithout having to change the peak of the transmission power, byincreasing or decreasing the pulse region of the chaotic signal.

The structure of the chaotic signal generator 30 will be explained indetail below, with reference to FIG. 4.

The modulator 11 generates a chaotic carrier by combining a chaoticsignal from the chaotic signal generator 30 with a data signal. Withreference to point (a) of FIG. 1, ‘0s’ and ‘1s’ of binary data bits areprovided to the modulator 11 in the form of pulse. By combining the datasignal with the chaotic signal, a chaotic carrier, which has a chaoticsignal only in the information region of the data signal, is generated(see point (e) of FIG. 1). FIG. 2D is a graphical representation showingan enlarged part of the chaotic carrier at point (e) of FIG. 1. Afterthe modulation, the frequency band of the chaotic carrier (see FIG. 2E)is same as that of the chaotic signal (see FIG. 2B). In other words,there is no relation between the pulse region of the chaotic signal andthe frequency bandwidth.

The reception circuit 20 may include a low noise amplifier (LNA) 21, adetector 23, an automatic gain control (AGC) amplifier 25, a LPF 27, andan analogue-to-digital (A/D) converter 29.

The LNA 21 may amplify the chaotic carrier which is received over theantenna 5, and transmits the amplified signal to the detector 23.

The detector 23 detects the chaotic carrier and extracts a data signal.The detector 23 may include a diode, and as the chaotic carrier passesthe detector 23, the chaotic carrier forms curvy signal waves as shownin the graphical representation of point (c) of FIG. 1.

The AGC amplifier 25 may increase or decrease the rate of amplification,and amplifies the signal waves extracted by the detector 23 to apredetermined level. The LPF 27 may filter the amplified signal waves sothat the waves can be converted into digital signal at the A/D converter29.

The A/D converter 29 converts the signal waves into digital signal, andtherefore, extracts a data signal of pulse form as shown in FIG. 2B.

FIG. 4 is a block diagram of a chaotic signal generator of the RFcommunication system of FIG. 1.

The chaotic signal generator 30 may include a loop of a nonlinearelement 31, a first filter 33 and one or more filters 35, 37.

The nonlinear element 31 is a main part of an oscillator and operates toamplify an input signal of small power to an output signal of highpower. The output function f(z) of the nonlinear element 31 may beexpressed by Equation 1 as follows:

$\begin{matrix}{{f(z)} = {M\left\lbrack {{{z + e_{1}}} - {{z - e_{1}}} + \frac{{{z - e_{2}}} - {{z + e_{2}}}}{2}} \right\rbrack}} & (1)\end{matrix}$

where, M is an amplifier constant of the nonlinear element 31, and e₁,e₂ are constants.

A transistor or a diode may be used as the nonlinear element 31. Whenthe transistor is used, for example, a DC bias power to operate thetransistor is converted to high frequency power, thereby resulting inamplification. The nonlinear element 31 of the chaotic signal generator30 amplifies the noise inside the loop, and the amplified signalcirculates along the loop and inputted back to the nonlinear element 31.As the above process repeats, stable chaotic signal is outputted.

The first filter 33 receives high frequency power signal from thenonlinear element 31, and processes the received high frequency powersignal so that oscillation can occur. When a high frequency power signalis generated by amplifying a noise of the nonlinear element 31, the highfrequency power signal usually contains not only the frequency selectedduring the design process, but also a harmonic ingredient which ismultiple times larger than the selected frequency. The first filter 33may select from the high frequency power signal the range of harmonicingredient to be used for the oscillation. That is, the first filter 33may also operate to limit the frequency band of the chaotic signal, byselecting the frequency range to be used for the oscillation.

The first filter 33 may be a LPF. This will be explained below as oneexample of the present invention, and the first filter 33 will bereferred to as the first LPF 33. The first LPF 33 may be a primaryfilter, and the relation between the input and output of the first LPF33 may be expressed by Equation 2 as follows:

Tx ₁ ′+x ₁ =f(z _(N))  (2)

where, f(z_(N)) is the function of high frequency output from thenonlinear element 31, that is, the function of signal inputted to thefirst LPF 33, T is a time constant of the first LPF 33, and x₁ is theinitial signal outputted from the first LPF 33.

The chaotic signal generator 30 has to meet the following two conditionsas other general ring oscillators do. First, the signal passing theentire loop of the nonlinear element 31, the first filter 33 and thesecond filter 35, 37 should have a phase variance of 360 degrees, whichis a multiple of 2π. Second, the gain of the entire loop should begreater than ‘1’. Both the first and the second filters 33, 35, 37should meet the above conditions.

The second filter 35, 37 may include a plurality of second LPFs 35 and aplurality of BPFs 37, and like a resonator of the ring oscillator, thesecond filter 35, 37 operates to determine the bandwidth of theresonating frequency. The only difference is that while the resonatorselects and resonates one frequency, the second LPFs 35 and the BPFs 37of the chaotic signal generator 30 cause a plurality of frequencycomponents to be selected by passing the frequency of certainbandwidths. The BPFs 37 operate to determine resonating frequency bandto generate a chaotic signal in the desired frequency band, and thesecond LPFs 35, rather than determining the resonating frequency band,operate to enable oscillation by causing the signal passing the loop tohave a phrase variance as a multiple of 2π in cooperation with the BPFs37.

The second LPFs 35 and the BPFs 37 are secondary filters, which havehigher phase variance and larger and higher loop gains than the primaryfilters. Accordingly, the first LPF 33 may be employed as the primaryfilter, and the second LPFs 35 and the BPFs 37 may be employed as thesecondary filters. By using the primary and the secondary filtersappropriately, various frequency components can be selected.Additionally, because the second LPFs 35 and the BPFs 37 have differentphase variances, and the respective frequency components vary phasedifferently, a wider frequency band is obtained.

In one example, the second filters 35, 37 may include M number of secondLPFs 35. In this example, the first one 35 a of the second LPFs 35receives input from the first LPF 33. The relation between the input andoutput of the first one 35 a of the second LPFs 35 may be expressed byEquation 3 as follows:

y ₁″+α_(L1) y ₁′+ω_(L1) ² y ₁=ω_(L1) ² x ₁  (3)

where, x₁ is an output from the first LPF 33, that is, input to thefirst one 35 a of the second LPFs 35, α_(L1) is an attenuation constant,ω_(L1) is a resonating frequency, and y₁ is an output from the first one35 a of the second LPFs 35.

The relation between the input and output of the (M)th LPF 35 m of thesecond LPFs 35 may be expressed by Equation 4 as follows:

y _(M)″+α_(LM) y _(M)′+ω_(LM) ² y _(M)=ω_(LM) ² y _(M-1)  (4)

where, y_(M-1) is an output from the (M−1)th LPF of the second LPFs 35,that is, an input to the (M)th LPF 35 m, and y_(M) is an output from the(M)th LPF.

In another example, the second filters 35, 37 may include (n) number ofBPFs 37. In this example, the first BPF 37 a receives a signal outputtedfrom the (M)th LPF 35 m of the second LPFs 35, and the relation betweenthe input and output of the first BPF 37 a may be expressed by Equation5 as follows:

z ₁″+α_(B1) z ₁′+ω_(B1) ² z ₁=ω_(B1) ² y′ _(M)  (5)

where, y_(M) is an output from the (M)th LPF 35 m of the second LPFs,that is, an input to the first BPF 37 a, α _(B1) is an attenuationconstant, ω_(B1) is a resonating frequency, and z₁ is an output from thefirst BPF 37 a.

The relation between the input and output of the (N)th BPF 37 n may beexpressed by Equation 6 as follows:

z _(N)″+α_(BN) z′ _(N)+ω_(BN) ² z _(N)=ω_(BN) ² z _(N-1)′  (6)

where, z_(N-1) is an output from the (N−1)th BPF, that is, an input tothe (N)th BPF 37 n, and z_(N) is an output from the (N)th BPF 37 n.

The output signal from the BPFs 37 is inputted back to the nonlinearelement 31, and circulates along the loop of the first LPF 33, thesecond LPFs 35 and the BPFs 374 of the nonlinear element 31 to finallybecome stable chaotic signal.

FIG. 5 is a block diagram of a chaotic signal generator according to anexemplary embodiment of the present invention. As shown, the chaoticsignal generator according to one exemplary embodiment may include anonlinear element 131, a first LPF 133, a second LPF 135, and three BPFs137 a, 137 b, 137 c.

The nonlinear element 131 amplifies a DC bias power to high frequencypower, and the first LPF 133 filters the high frequency signal in thebase band.

The resonating frequency band is determined when the high frequencysignal filtered at the base band passes through the second LPF 135 andthe three BPFs 137 a, 137 b, 137 c. When the resonating frequency bandis determined, the signal is inputted back to the nonlinear element 131,and processed repeatedly to become a chaotic signal having a pluralityof frequency components.

The chaotic signal generated by the chaotic signal generator 130 shows aseries of pulses of different amplitudes and periods in time domain (seeFIG. 6).

FIG. 7 shows in a graphical representation the result of measuring apower spectrum density of the chaotic signal according to an exemplaryembodiment of the present invention.

With reference to FIG. 7, 99% of power of the power spectrum is focusedaround −20 dB, which means high energy rate and low power consumption.

FIG. 8A is a graphical representation of an example of a signal maskdefined by the FCC, and FIG. 8B shows a power spectrum of chaotic signalgenerated by a chaotic signal generator based on the mask of FIG. 8A. Asshown, the power spectrum of the chaotic signal from the chaotic signalgenerator 130 almost matches the FCC signal mask.

FIG. 9A is a graphical representation of time domain of chaotic carrierwhich combines the chaotic signal of FIG. 6 with the data signal, andFIG. 9B is a power spectrum of chaotic carrier of FIG. 9A.

While the chaotic signal of FIG. 6 is successively formed in timedomain, the chaotic carrier of FIG. 9A shows a chaotic signal appearingand disappearing according to the data signal. Both of FIGS. 8B and 9Bshow almost no difference of power spectrum between before and after thechaotic signal is combined with the data signal.

Because there is almost no change in the power spectrum by the fact thatthe data signal is combined, or not combined with the chaotic signal,most of the RF communication system can still be utilized after thecombination of signals.

As explained above, according to the exemplary embodiments of thepresent invention, a transmission circuit of an RF communication systemdoes not need to use additional components such as VCO, PLL andup-mixer, and a reception circuit also does not need to employcomponents such as down-mixer. Additionally, a diode may be used as adetector in constructing a wideband RF communication system. Because thepower consumption can be greatly reduced, a low rate RF communicationsystem can be provided, and the size of the RF communication system isalso reduced. Additionally, price can be reduced, and RF communicationsystem becomes easy to construct. Also importantly, a power efficiencyis high because the chaotic signal generator has 99% of power spectrumaround −20 dB within the FCC standard mask.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Also, thedescription of the embodiments of the present invention is intended tobe illustrative, and not to limit the scope of the claims, and manyalternatives, modifications, and variations will be apparent to thoseskilled in the art.

1. A radio frequency (RF) communication system comprising: a chaoticsignal generator which generates a chaotic signal having a plurality offrequency components at a predetermined frequency band; a modulatorwhich generates a chaotic carrier by combining the chaotic signal with adata signal; and a transmission circuit comprising an antenna totransmit the chaotic carrier generated by the modulator.
 2. The RFcommunication system of claim 1, wherein the chaotic signal generatorcomprises an oscillator which converts a direct current (DC) bias powerinto the high frequency power, and a resonating unit which generates awideband signal having a plurality of frequency components by passingthe predetermined frequency band of the high frequency power signal. 3.The RF communication system of claim 2, wherein the resonating unitcomprises: a first filter which receives the high frequency power fromthe oscillator and passes at least a part of a harmonic signal of thehigh frequency power as a filtered signal; and a second filter whichgenerates the wideband signal having the plurality of frequencycomponents of the predetermined range of frequency band by oscillatingthe filtered signal, and provides the oscillator with the widebandsignal.
 4. The RF communication system of claim 3, wherein theoscillator comprises a nonlinear element, and high frequency power ofthe nonlinear element is determined by:${f(z)} = {M\left\lbrack {{{z + e_{1}}} - {{z - e_{1}}} + \frac{{{z - e_{2}}} - {{z + e_{2}}}}{2}} \right\rbrack}$wherein, M is an amplifier constant of the nonlinear element, and e₁, e₂are constants.
 5. The RF communication system of claim 4, wherein thenonlinear element comprises one of a transistor and a diode.
 6. The RFcommunication system of claim 5, wherein the chaotic signal generatorenables oscillation if a phase variance of a signal passing a loop ofthe nonlinear element, the first filter and the second filter is amultiple of 2π.
 7. The RF communication system of claim 6, wherein thechaotic signal generator additionally enables the oscillation if a totalgain of the loop is larger than
 1. 8. The RF communication system ofclaim 3, wherein the signal outputted from the first filter isdetermined by:Tx ₁ ′+x ₁ =f(z _(N)) wherein, f(z_(N)) is a function of high frequencyoutput from the oscillator, T is a time constant of the first filter,and x₁ is an initial signal outputted from the first filter.
 9. The RFcommunication system of claim 8, wherein the first filter comprises alow pass filter (LPF).
 10. The RF communication system of claim 9,wherein the first filter is a primary filter.
 11. The RF communicationsystem of claim 1, wherein the second filter comprises at least one bandpass filter (BPF).
 12. The RF communication system of claim 11, whereinthe BPF is a secondary filter.
 13. The RF communication system of claim11, wherein the second filter comprises a plurality of N BPFs and an(N)th output from an (N)th BPF is determined by:z _(N)″+α_(BN) z′ _(N)+ω_(BN) ² z _(N)=ω_(BN) ² z _(N-1)′ wherein,z_(N-1) is an output from an (N−1)th BPF, that is, an input to the (N)thBPF, α_(BN) is an attenuation constant, ω_(BN) is a resonating frequencyand z_(N) is an output from the (N)th BPF.
 14. The RF communicationsystem of claim 13, wherein the plurality of N BPFs determines aresonating frequency band of the chaotic signal generator.
 15. The RFcommunication system of claim 1, wherein the second filter comprises atleast one LPF.
 16. The RF communication system of claim 15, wherein theLPF of the second filter is a secondary filter.
 17. The RF communicationsystem of claim 16, wherein the second filter further comprises a bandpass filter (BPF) and the LPF of the second filter is disposed betweenthe first filter and the BPF.
 18. The RF communication system of claim17, wherein the second filter comprises a plurality of M LPFs and anoutput from an (M)th LPF of the second filter is determined by:y _(M)″+α_(LM) y _(M)′+ω_(LM) ² y _(M)=ω_(LM) ² y _(M-1) wherein,y_(M-1) is an output from an (M−1)th LPF, that is, an input to the (M)thLPF, α_(LM) is an attenuation constant, ω_(LM) is a resonatingfrequency, and y_(M) is an output from the (M)th LPF.
 19. The RFcommunication system of claim 18, wherein the plurality of M LPFs andthe BPF of the second filter have different delayed phase widths andgains.
 20. The RF communication system of claim 19, wherein the BPF is apredetermined number of BPFs so that a phase of a signal passing a loopof the oscillator, the first filter and the second filter corresponds toa multiple of 2π.
 21. A radio frequency (RF) communication systemcomprising: a nonlinear element which converts a direct current (DC)bias power into a high frequency power; a first low pass filter (LPF)which filters the high frequency power into a predetermined frequencyband; at least one second LPF which shifts the filtered high frequencypower according to a predetermined phase width to generate a shiftedsignal; and at least one band pass filter (BPF) which has a differencephase width than the at least one second LPF, and filter the shiftedsignal into a predetermined frequency band.
 22. The RF communicationsystem of claim 21, wherein the at least one BPF comprises a first BPF,a second BPF and a third BPF.
 23. A radio frequency (RF) communicationsystem comprising: an oscillator which converts a direct current (DC)bias power into a high frequency power; and a resonating unit whichgenerates a wideband signal having a plurality of frequency componentsby passing a predetermined frequency band of the high frequency powersignal.
 24. A radio frequency (RF) communication system comprising: anonlinear element which converts a direct current (DC) bias power into ahigh frequency power; a first filter which receives the high frequencypower from the nonlinear element and passes at least a part of aharmonic signal of the high frequency power; and a second filtercomprising at least one low pass filter (LPF) and at least one band passfilter (BPF), which generates a wideband signal having a plurality offrequency components in a predetermined range of frequency band byoscillating a signal from the first filter, and provides the nonlinearelement with the wideband signal.
 25. A radio frequency (RF)communication system comprising: a nonlinear element which converts adirect current (DC) bias power into a high frequency power; a firstfilter which receives the high frequency power from the nonlinearelement and passes at least a part of a harmonic signal of the highfrequency power; and at least one second filter which generates awideband signal having a plurality of frequency components in apredetermined range of frequency band by oscillating a signal from thefirst filter, and provide the nonlinear element with the widebandsignal.
 26. A radio frequency (RF) communication system comprising: anonlinear element which converts a direct current (DC) bias power into ahigh frequency power; a first filter which receives the high frequencypower from the nonlinear element and passes at least a part of aharmonic signal of the high frequency power; and a second filtercomprising one or more LPFs and one or more BPFs which generates awideband signal having a plurality of frequency components in apredetermined range of frequency band by oscillating a signal from thefirst filter, and provides the nonlinear element with the widebandsignal.
 27. A method of generating a chaotic signal in a radio frequency(RF) communication system, the method comprising: converting a directcurrent (DC) bias power into a high frequency power; generating aninitial signal which meets initial conditions for oscillation using thehigh frequency power; and generating a wideband signal having aplurality of frequency components in a predetermined range of frequencyband by oscillating the initial signal.
 28. The method of claim 27,wherein the high frequency power is generated by:${f(z)} = {M\left\lbrack {{{z + e_{1}}} - {{z - e_{1}}} + \frac{{{z - e_{2}}} - {{z + e_{2}}}}{2}} \right\rbrack}$wherein, M is an amplifier constant of a nonlinear element, and e₁, e₂are constants.
 29. The method of claim 28, wherein the nonlinear elementcomprises a transistor.
 30. The method of claim 27, wherein a loop isgenerated during the process of converting the DC bias power into thewideband signal and a phase of a signal passing the loop corresponds toa multiple of 2π in order for the oscillating to occur.
 31. The methodof claim 27, wherein a total gain of the loop is larger than 1 in orderfor the oscillating to occur.
 32. The method of claim 27, wherein theinitial signal is determined by:Tx ₁ ′+x ₁ =f(z _(N)) wherein, f(z_(N)) is a function of high frequencyoutput from a nonlinear element, T is a time constant of a first filter,and x₁ is an initial signal outputted from the first filter.
 33. Themethod of claim 32, wherein the first filter comprises a low pass filter(LPF).
 34. The method of claim 33, wherein the first filter is a primaryfilter.
 35. The method of claim 27, wherein the second filter comprisesat least one band pass filter (BPF).
 36. The method of claim 35, whereinthe BPF is a secondary filter.
 37. The method of claim 35, wherein thesecond filter comprises a plurality of N BPFs and an (N)th output fromthe (N)th BPF is determined by:z _(N)″+α_(BN) z _(N)′+ω_(BN) ² z _(N)=ω_(BN) ² z _(N-1) wherein,z_(N-1) is an output from an (N−1)th BPF, that is, an input to the (N)thBPF, α_(BN) is an attenuation constant, ω_(BN) is a resonating frequencyand z_(N) is an output from the (N)th BPF.
 38. The method of claim 37,wherein the second filter comprises at least one LPF.
 39. The method ofclaim 38, wherein the LPF of the second filter is a secondary filter.40. The method of claim 39, wherein the LPF of the second filter isdisposed between the first filter and the plurality of N BPFs.
 41. Themethod of claim 40, wherein the second filter comprises a plurality ofM, LPFs and an output from an (M)th LPF of the second filter isdetermined by:y _(M)″+α_(LM) y _(M)′+ω_(LM) ² y _(M)=ω_(LM) ² y _(M-1) wherein,y_(M-1) is an output from an (M−1)th LPF, that is, an input to the (M)thLPF, α_(LM) is an attenuation constant, ω_(LM) is a resonatingfrequency, and y_(M) is an output from the (M)th LPF.
 42. The method ofclaim 41, wherein the plurality of M LPFs and the plurality of N BPFs ofthe second filter have different delay phase widths and gains.
 43. Themethod of claim 42, wherein N and M are predetermined numbers so that aphase of a signal passing a loop of the nonlinear element, the firstfilter and the second filter corresponds to a multiple of 2π.
 44. Themethod of claim 27, wherein the wideband signal comprises a chaoticsignal having the plurality of frequency components in the predeterminedrange of frequency band.